To be honest though building a processor these days is not exactly difficult. That is especially true if you start with someone else's ISA and they have already created a GCC or LLVM back end for it. I was at Sun during the development of SPARC and as part of the Systems group we got to see a lot of the trade offs up front but these days transistors are not nearly so scarce. If you stick to 30 - 50Mhz for your first round you can simulate pretty much power on to shell prompt in a reasonable amount of time. Then there are the process specific issues that TSMC or Global Foundries or whomever will help you with translating your HDL into their most reliable node (probably 45nm or 90nm at the moment), then you'll build a test chip and it will likely do everything you want it to do and it will cost 10x what an equally powerful ARM chip will do, so you will really really want to use your chip instead of that one if you're going to design it into something. And that something has to be popular enough that you sell at least a million of them, otherwise you're going to eat a lot of Nonrecurring engineering (NRE) cost.
It is certainly possible, but it is a long game and you have to survive the early years. Go back and read the history of ARM (and Acorn), Intel (and IBM), Motorola (and Sun and Apple), and Power PC (and Cisco). Then read the history of the Z8000, the NS32032, the AMD88000, and the TI 9900. When you look at the history from where we sit today you will see that building a new CPU is the easiest thing in the world, staying alive until it is relevant is exceptionally difficult and requires quite a bit of luck in addition to good design.
I wish these guys a lot of luck, I would love to see a fully open architecture be even half as successful as ARM has been. They have to walk into this with their eyes open though, it is not going to be easy.